Various known rear steering apparatuses each serving as a part of a four-wheel steering system of a vehicle are disclosed. For example, JP5098242B (i.e., hereinafter referred to as Patent reference 1) discloses a basic structure that includes a rod connected to rear wheels of a vehicle, a housing supporting the rod and fixed to a chassis of the vehicle, and a motor housed in the housing and actuating the rod for steering the rear wheels. There are various types of suspension mechanisms for supporting rear wheels of a vehicle and thus types of the rear wheel steering apparatus mounted to the suspension mechanism are varied. For example, JP2012-511465A (i.e., hereinafter referred to as Patent reference 2) discloses an apparatus that includes a blocking device for selectively transmitting a drive force from an electric motor to a push rod and the blocking device is supported by a module housing together with the electric motor and a transmission that is for converting a rotation of the electric motor to a translation of the push rod. Patent reference 2 further discloses a control unit for controlling the electric motor, the blocking device, and the transmission.
According to the apparatus disclosed in Patent reference 2, because the electric motor, the transmission and the blocking device are supported by the module housing, assembling is difficult. Further, according to the apparatus disclosed in Patent reference 2, because the housing is required to have high mechanical strength, it is difficult to downsize the housing. Patent reference 2 discloses an electric interface that forms a portion of a circuit board of the control unit. Patent reference 2 further discloses an external electric interface for an outgoing cable extending to a bus line of a CAN of the vehicle or a brake control unit. The external electric interface is connected to the control unit while being joined to a cover. Thus, according to the construction disclosed in Patent reference 2, the module housing and the cover are needed to be joined with water-proof joining structure and further, the cover and the external electric interface are needed to be joined with water-proof joining structure. Further, according to the construction disclosed in Patent reference 2, a water-proof connecter is required for connecting the control unit to the cable. On the other hand, regarding the construction of Patent reference 1, because a controller (control unit) for controlling the actuation of the motor, for example, is generally disposed within a case and mounted to the housing, a water-proof joining structure is provided between the case and the housing and a water-proof connecter is applied for joining the controller to a cable including a power line and a signal line. Because large-sized and high-priced water-proof connecter is required for the apparatuses disclosed in Patent reference 1 and Patent reference 2 in addition to providing the water-proof joining structure of the housing, for example, a manufacturing cost increases.
A need thus exists for a rear wheel steering apparatus for a vehicle which is not susceptible to the drawback mentioned above.